Ring-shaped air distribution disc and an air distribution device having such an air distribution disc

ABSTRACT

A ring-shaped air distribution disc (11) for an air distribution device for providing rinsing air to an air cleaner provided with filter bags is provided. The ring-shaped air distribution disc (11) has a width that slightly exceeds the diameter (d) of at least one aperture (2) for rinsing air. In use the ring-shaped air distribution disc (11) is suspended in a free floating manner in the air distribution device, and is pressed against sealing means (5) of a number of rinsing air tubes (4) by springs (15) supported by a supporting plate (8) positioned underneath the ring-shaped air distribution disc (11).

The invention relates to an air distribution-disc for the distributionof rinsing air in an air cleaner provided with filter bags, and to anair distribution device has having such an air distribution disc.

An air distribution disc is used in for instance an air cleaner of thetype disclosed in U.S. Pat. No. 4,220,457 showing a cyclone comprising acylindrical housing with tangential entrance for dust-containing air.The lower end of the cylindrical housing of the cyclone is tapered isprovided with a dust collector. The opposite upper end of thecylindrical housing is divided by an intermediary wall into a lowerdust-containing chamber and an upper dust-free chamber. Filter bags aresuspended from the intermediary wall extending into the dust-containingchamber, the filter bags being closed at their lower ends and open attheir upper ends.

In use the dust-containing air enters the cyclone via the tangentialentrance and large particles are separated off in the cyclone. Smallerdust particles flow upwards with the air in the dust-containing chamber.The dust-containing air enters the filter bags from the outside causingthe dust to deposit on the filter bags. The now cleaned air flowsfurther upwards within the filter bags into the dust-free chamber andleaves the air cleaner via an outlet for clean air provided in thedust-free chamber.

After some time of filtering the filter bags may have a rather largeamount of dust deposited on their outer surfaces. In order to remove thedeposited dust, rinsing air is blown through the filter bags incountercurrent, i.e. from the dust-free chamber to the dust-containingchamber through the filter bags.

U.S. Pat. No. 4,220,457 discloses an arrangement for controlling theblowing of rinsing air in such a way that the filter bags arealternately rinsed during operation. The arrangement comprises a plane,disc-shaped air distribution disc having two diametrically oppositeapertures. The air distribution disc is positioned over the upper endsof the filter bags, and the two apertures in the air distribution discare arranged such that they alternately, by rotation of the airdistribution disc, is aligned with the filter bags. Above the airdistribution disc, tubes for rinsing air is provided, one tubing foreach filter bag. The tubes are connected to a device for compressed air.

In use the air distribution disc is rotated slowly, causing filter bagsto be rinsed by compressed air in countercurrent each time the aperturesof the air distribution disc are aligned with the rinsing air tubes andthe filter bags.

The air distribution disc should be in sealing engagement with therinsing air tubes in order to prevent any leakage of rinsing air whenthe tubes are not aligned with the apertures of the air distributiondisc. In use, however, practice has shown that the sealing engagement ishard to maintain due to the friction between the air distribution discand the sealing surface of the tubes. In fact, the friction between theair distribution disc and the sealing surface of the tubes provokes theair distribution disc to expand, especially in the area around theapertures, butt since the air distribution disc is an almost closeddisc, the outer area of the air distribution disc tends to bend out ofthe plane of the air distribution disc, causing a gap to arise betweenthe air distribution disc and the sealing surface of the rinsing airtubes. A large amount of rinsing air may be lost because of this gap.This problem is even worse when hot air is rinsed, due to the hightemperatures.

A solution to this problem has been to provide a rigid supporting plateunderneath the air distribution disc, supporting the air distributiondisc by rubber supports between the supporting plate and the airdistribution disc, trying to force the air distribution disc not to bendout. This solution has the disadvantage that when the sealing means ofthe rinsing air tubes are worn, the same problem as described abovereappears. Further, the rubber supports are not suitable when rinsinghot air.

Another solution is to reduce the diameter of the apertures, causinglesser expansion of the air distribution disc but requiring higherrinsing air pressure.

It is an object of the present invention to provide air distributiondisc that does not suffer from the disadvantages mentioned above and animproved air distribution device having such an air distribution disc.

According to the invention this is achieved by arranging the airdistribution disc as stated in claim 1 and by arranging the airdistribution device as stated in claim 4.

By shaping the air distribution disc as a ring having a width that isslightly larger than the diameter of the at least one aperture, acompliant air distribution disc is provided. This has the advantage thatit does not tend to bend out of its plane when stressed, since it canexpand more freely than is the case with an almost closed disc accordingto the prior art. The sealing between the ring-shaped shaped airdistribution disc and the sealing means of the rinsing air tubes cantherefore be more securely maintained.

Furthermore, the apertures may have a rather large diameter, whereby lowpressure rinsing air may be utilised.

In use the ring-shaped air distribution disc is preferably free floatingin order to maintain its compliance stresses. This is achieved bysupporting the ring-shaped air distribution disc in a central supporthaving an annular groove in which the ring-shaped air distribution discis suspended in a free floating manner. Preferably the central hole ofthe ring-shaped air distribution disc is provided with notches which areengagable with supporting means provided in the annular groove of thecentral support.

In order to seal the ring-shaped air distribution disc against thesealing means of the rinsing air tubes, a supporting plate is providedunderneath the ring-shaped air distribution disc, said supporting platebeing provided with springs for pressing the ring-shaped airdistribution disc against the sealing means of the rinsing air tubes.

The free floating air distribution disc and the use of springs forpressing the air distribution disc against the sealing means of therinsing air tubes further ensures that the ring-shaped air distributiondisc and the sealing means of the rinsing air tubes are in sealingcontact even when the sealing means of the rinsing air tubes becomesworn.

Preferably the ring-shaped air distribution disc is made of steel, butother materials may be used as well.

The invention will now be discussed in further detail with reference tothe accompanying drawings in which

FIG. 1a shows a part of an air distribution device according to theprior art with the air distribution disc in its closed position,

FIG. 1b shows the same as FIG. 1a with the air distribution disc in itsopened position,

FIG. 2a shows a part of another air distribution device according to theprior art with the air distribution disc in its closed position,

FIG. 2b shows the same as FIG. 2a with a stressed distribution disc,

FIG. 3a is a side view of a stressed air distribution disc according tothe prior art,

FIG. 3b shows a top plan view of an air distribution disc according tothe prior art,

FIG. 4a is a side view of an air distribution di t, according to thepresent invention,

FIG 4b shows a top plan view of an air distribution disc according tothe present invention, and

FIG. 5 shows a part of an air distribution device provided with an airdistribution disc according to the present invention in its closedposition.

FIG. 1a shows a part of an air distribution devices according to priorart with an air distribution disc 1 provided with an aperture 2 near theouter edge 3. Above the air distribution disc 1, a rinsing air tube 4 isshown, the rinsing air tube having a sealing means 5, preferably made ofrubber, which is during operation pressed against the air distributiondisc 1. A flow of rinsing air 6 is indicated by the dotted lines.

Normally the air cleaner is provided with a large number of filter bags,e.g. up to 300, and a corresponding number of rinsing air tubes 4 may bealigned with the filter bags. Alternatively, the air distribution deviceis constructed as a rotatable unit having only a few, e.g. 7-10, rinsingair tubes 4, which, during rotation of the air distribution device, arealternately aligned with the same number of filter bags. In the Figures,however, only single rinsing air tube 4 is shown for illustrating thefunctionality of the air distribution disc 1.

The air distribution disc 1 is circular as shown in FIG. 3b with anouter radius R and is provided with a central hole 7 with a radius r.The aperture 2 arranged near the outer edge 3 has a diameter dcorresponding to the diameter of the rinsing air tube 4.

The air distribution device in FIG. 1a is shown in its opened position,i.e. rinsing air 6 is flowing through >s aperture 2 and further into afilter bag (not shown) positioned underneath the air distribution disc 1for rinsing the filter bag with air in countercurrent.

FIG. 1b shows the same air distribution device as FIG. 1a, but in itsclosed position, since the air distribution disc 1 is rotated such thatthe aperture 2 is no longer aligned with the rinsing air tube 4.

Due to the friction between the air distribution disc 1 and the sealingmeans 5 of the rinsing air tubes 4, the air distribution disc 1 tends tobend out of its plane and assume the shape shown in FIG. 3a, therebyincreasing the risk of leakage between the air distribution disc 1 andthe rinsing air tubes 4.

In order to minimise this risk, a thick supporting plate 8 may beprovided underneath the thin air distribution disc 1 as shown in FIG.2a. This also known in the prior art.

The supporting plate 8 is provided with elastic rubber supports 9 inorder to force the air distribution disc 1 into sealing engagement withthe sealing means 5 of the rinsing air tubes 4. In order to furtherminimise the risk of air leakage, the diameter of the rinsing air tubes4 may be reduced and the air pressure increased.

Despite of this improved air distribution device, leakage may occurespecially when hot dust-containing air is to be cleaned. The higher thetemperature, the greater the risk that the air distribution disc 1 bendsout of its plane and compresses the elastic rubber supports 9 as shownin FIG. 2b, creating a small gap 10 between the air distribution disc 1and the sealing means 5 of the rinsing air tube 4.

Besides, the elastic rubber supports 9 are not suitable for use in hightemperature conditions.

A ring-shaped air distribution disc 11 according to the invention isshown in FIGS. 4a and 4b. FIG. 4a shows the ring-shaped air distributiondisc 11 from the side, and it can be seen that the ring-shaped airdistribution disc 11 consists of a thin, planar disc, preferably made ofsteel.

In FIG. 4b the ring-shaped air distribution disc 11 is shown in a topplan view. The ring-shaped air distribution disc 11 has an outer radiusR, an inner central hole 7 with a radius r and an aperture 2 with adiameter d. The aperture 2 is positioned midways in the ring defined bythe outer radius R and the inner radius r, leaving only a slim piece ofmaterial between the aperture 2 and the outer edge 3 and between theaperture 2 and the central hole 7.

Since the air distribution disc 11 is ring-shaped it does not tend tobend out to the same degree as a disc-shaped air distribution disc 1.This is due to the fact that the ring-shaped air distribution disc 11 ismore compliant to stresses while maintaining its planar shape than analmost closed air distribution disc. In other words, the ring-shaped airdistribution disc 11 expands more freely outwards, having no need forbending out of the plane.

The notches 12 in the central hole 7 are used when mounting thering-shaped air distribution disc 11 in the air distribution device.

FIG. 5 shows the ring-shaped air distribution disc 11 mounted in an airdistribution device in its closed position.

The air distribution device again comprises a rinsing air tube 4 withsealing means 5 which seals the rinsing air tube 4 against thering-shaped air distribution disc 11. The air distribution devicefurther comprises a central support 13 for the ring-shaped airdistribution disc 11, said central support 13 having an annular groove14 at its outer edge. The ring-shaped air distribution disc 11 isarranged free floating in the annular groove 14, unless for engagingmeans (not shown) in the annular groove 14, engaging the notches 12 ofthe ring-shaped air distribution disc 11. The double arrows A and Bindicate the free floating directions of the ring-shaped airdistribution disc 11.

In order to press the ring-shaped air distribution disc 11 against thesealing means 5 of the rinsing air tube 4, a supporting plate 8 isarranged underneath the ring-shaped air distribution disc 11 and springs15 are arranged between the supporting plate 8 and the ring-shaped airdistribution disc 11. By using springs 15 instead of rubber supports 9,an air distribution device which is more suitable for rinsing hot air isprovided.

What is claimed is:
 1. An air distribution disc (11) for an airdistribution device for providing rinsing air to an air cleaner providedwith filter bags, said air distribution disc (11) consisting of arotatable, substantially circular, plate having an outer edge (3) withan outer radius (R) and a substantially circular inner central hole (7)with an inner radius (r), at least one aperture (2) having a diameter(d) being provided near the outer edge (3) between the outer edge (3)and the inner central hole (7), characterized in that the differencebetween the outer radius (R) and the inner radius (r) slightly exceedsthe diameter (d) of the at least one aperture (2).
 2. An airdistribution disc according to claim 1, characterized in that the innercentral hole (7) is provided with notches (12).
 3. An air distributiondisc according to claim 1, characterized in that it is made of steel. 4.An air distribution device for providing rinsing air to an air cleanerprovided with filter bags, said air distribution device comprising a airdistribution disc (11) consisting of a substantially circular, platehaving an outer edge (3) with an outer radius (R) and a substantiallycircular inner central hole (7) with an inner radius (r), at least oneaperture (2) having a diameter (d) being provided near the outer edge(3) between the outer edge (3) and the inner central hole (7), a centralsupport (13) for the air distribution disc (11), and at least onerinsing air tube (4), said rinsing air tube (4) being provided withsealing means (5), sealing the rinsing air tube (4) against the airdistribution disc (11), characterized in that the difference between theouter radius (R) and the inner radius (r) of the air distribution disc(11) slightly exceeds the diameter (d) of the at least one aperture (2)in the air distribution disc (11), that the air distribution disc (11)is suspended in a free floating manner in the central support (13), andthat a supporting plate (8) provided with at least one spring (15) forpressing the air distribution disc (11) against the sealing tube (4) isarranged underneath the air distribution disc (11).
 5. An airdistribution device according to claim 4, characterized in that thecentral support (13) is provided with an annular groove (14) in whichthe air distribution disc (11) is suspended in a free floating manner.6. An air distribution device according to claim 5, characterized inthat the inner central hole (7) of the air distribution disc (11) isprovided with notches (12) that co-operate with engaging means in theannuls. groove (14).
 7. An air distribution device according to claim 4,characterized in that the air distribution disc (11) is made of steel.